IT201800009327A1 - Process for the preparation of compounds for tires and tires that include them - Google Patents

Description

DESCRIPTION

attached to a patent application for an INDUSTRIAL INVENTION PATENT entitled:

“PROCESS FOR THE PREPARATION OF COMPOUNDS FOR E TIRES

TIRES THAT UNDERSTAND "

DESCRIPTION

FIELD OF THE INVENTION

The present invention relates to a process for the preparation of elastomeric compounds for tires with a reduced zinc content, characterized by the incorporation of particular charges activating the vulcanization and by a precise sequence of adding some components of the compound.

STATE OF THE TECHNIQUE

In the tire industry, vulcanization is a process commonly used to improve the mechanical properties of natural rubber or unsaturated polymers, a process that affects the hardness, elasticity, hysteresis of the material at different temperatures and, consequently, its behavior. of the tire in the wet as well as the friction and abrasion of the same during use. Over the years, various additives have been proposed to improve the vulcanization process as vulcanization activators and accelerators.

In general, with these additives, it is desired to increase the degree and homogeneity of the crosslinking while decreasing the energy and time required to complete the reaction.

The main vulcanization activators, capable of increasing the efficiency of the process, are inorganic compounds such as metal oxides and hydroxides, for example ZnO, MgO, Ca (OH) 2.

Among the various activators, zinc oxide ZnO is considered the most efficient and is still used today in many vulcanization processes. This activator is used in combination with weak organic acids (e.g. stearic acid) which promote its activity within the rubber.

Some studies - see for example the article by Y. Ikeda, et al. Dinuclear bridging bidentate zinc / stearate complex in sulfur cross-linking of rubber, Macromolecules 48 (2015) 462–475) - have suggested that Zn <2+> ions, generated by the interaction of ZnO with stearic acid, interact with the accelerator and sulfur molecules forming organo-metal complexes that would act as more efficient sulfur agents. A hypothesis of the structure of these complexes is illustrated in Figure 3 of this description.

The ability of Zn <2+> to form these complexes is a key element of the vulcanization process and strongly depends on the dispersion of ZnO within the polymer matrix, in turn influenced by both the particle size and the crystalline structure of the oxide. zinc.

Typically, in the vulcanization processes of tires for tires, microcrystalline ZnO is used as activator which, however, does not easily disperse in the polymeric matrix and reacts only partially with the other vulcanization agents.

The poor dispersibility and reactivity of the microcrystalline zinc oxide in the elastomeric compound inevitably leads to its overdosing compared to the amount actually required for crosslinking.

During the use of the tire, especially due to abrasion on the asphalt of the tread, the zinc present in the compounds is partially released.

Therefore, out of respect for the environment, over the years efforts have been made to decrease the amount of zinc in the compounds.

For example, we tried to use finer ZnO (nanometric particles) but the dispersion was still difficult for the formation of aggregates within the polymer matrix, effectively canceling the dimensional advantage over microcrystalline zinc oxide.

On the other hand, the use of compounds consisting of zinc oxide nanoparticles directly linked to silica nanoparticles, compounds having the dual function of reinforcing and activating the vulcanization (here for brevity indicated generically as activating fillers or specifically as ZnO / SiO2) (see articles A. Susanna et al. ZnO nanoparticles anchored to silica filler. A curing accelerator for isoprene rubber composites, Chemical Engineering Journal 275 (2015) 245–252) and A. Susanna et al., Catalytic effect of ZnO anchored silica nanoparticles on rubber vulcanization and cross-link formation, European Polymer Journal 93 (2017) 63–74).

According to the authors, compared to conventional microcrystalline ZnO, these activating fillers lead to a higher efficiency of vulcanization, which implies a) a faster reaction of ZnO with stearic acid and vulcanization agents to form more reactive sulfur complexes, b ) a greater cross-linking in the mixture with a more homogeneous distribution of the bonds and preferential formation of mono- and disulfide bridges between the polymer chains and, finally, c) a more homogeneous dispersion of the nanoparticles with the absence of aggregates of unreacted ZnO inside the matrix polymer, at the end of the vulcanization process. All these aspects candidate the aforementioned activating fillers to be promising substitutes for microcrystalline zinc oxide in the vulcanization of tire compounds, allowing a lower use of zinc, with important implications for environmental sustainability.

SUMMARY OF THE INVENTION

The Applicant has undertaken studies to further improve the effectiveness of the activating fillers described above in the production of compounds for tires, with the aim of further reducing the zinc content for vulcanization and, therefore, containing the environmental pollution from the release of zinc, and at the same time maintaining or possibly improving the process conditions, the yields and above all the properties of the final elastomeric compounds.

Surprisingly, the Applicant has found that if in the process of preparing the mixture the order of addition of some additives is suitably defined, in particular by introducing the compatibilizing agent (silane) only after the completion of the reaction between the activating charge (ZnO / SiO2 ) and fatty acid (stearic acid) it is possible to achieve the desired goals.

The Applicant has verified that, in addition to reducing the time and energy required for vulcanization, the compounds thus prepared, with the same content of activating fillers and zinc, have a better cross-linking.

In addition, the hysteretic properties shown by these compounds allow to predict in general lower rolling resistance and better resistance to abrasion as well as, in the eventual tread application, a possible better grip on the wet tire.

Furthermore, with the same performance or even better performance, the quantity of activating filler and, ultimately, of zinc in the compounds can be reduced, thus reducing the release of this metal at the environmental level.

A first aspect of the present invention is a process for the preparation of a vulcanizable elastomeric compound for tires, said process comprising at least:

- a mixing step (1) of at least one elastomeric polymer (A) and of at least one additive for elastomeric blends, with the exception of vulcanizing agents (B), to give a non-vulcanizable elastomeric blend;

- a mixing step (2) of the non-vulcanizable elastomeric blend and at least one vulcanizing agent (B), to give a vulcanizable elastomeric blend, and

- an unloading phase of the vulcanizable elastomeric compound,

wherein in the mixing steps (1) and / or (2) at least one fatty acid (C), at least one compound (D) comprising zinc directly bound to a white filler and at least one compatibilizing agent (E) are added,

characterized in that said at least one compatibilizing agent (E), is added after the complete addition and processing, of said at least one fatty acid (C) and at least one compound (D) comprising zinc directly bound to a white filler.

A second aspect of the present invention is represented by a vulcanizable elastomeric blend obtained according to the process of the first aspect of the present invention.

A third aspect of the present invention is represented by a tire component comprising the vulcanizable compound of the second aspect of the invention or the vulcanized compound obtained by its vulcanization.

A fourth aspect of the present invention is represented by a tire for vehicle wheels comprising a component in accordance with the third aspect of the invention.

DEFINITIONS

For the purposes of this description and of the claims that follow, the term "phr" (parts per hundreds of rubber) means the parts by weight of a given component of the elastomeric composition per 100 parts by weight of the diene elastomeric polymer.

Unless otherwise indicated, all percentages are expressed as percentages by weight.

In the present description, the term "elastomeric polymer" or "rubber" or "elastomer" means a natural or synthetic polymer which, after vulcanization, at room temperature can be repeatedly stretched to at least double its original length and which after removal of the tensile load returns substantially immediately and forcefully to its approximately original length (according to the definitions of ASTM D1566-11 Standard terminology relating to Rubber).

In the present description, the term "reinforcing filler" indicates a reinforcing material typically used in the sector to improve the mechanical properties of tire rubbers, preferably chosen from carbon black, conventional silica, such as silica from sand precipitated with strong acids, preferably amorphous, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina, aluminosilicates, kaolin, silicate fibers and their mixtures.

In the present description, the term "white filler" indicates a conventional reinforcement material used in the sector selected from conventional silica and silicates, such as sepiolite, paligorskite also known as attapulgite, montmorillonite, alloisite and the like, possibly modified by acid treatment and / or derivatized . Typically the white fillers have surface hydroxyl groups.

In the present description, the term "activating the vulcanization" indicates a compound capable of facilitating the vulcanization, making it take place in times and possibly at lower temperatures.

In the present description, the terms "activating filler" or "compound (D) comprising zinc directly bound to a white filler" are used interchangeably and indicate a compound capable of simultaneously reinforcing the compound and activating the vulcanization , formed by a white filler and a zinc compound in which the zinc is directly bound to the surface hydroxyl groups of the filler. In particular, as indicated in the article by A. Susanna et al, Chemical Engineering Journal 275 (2015) 245–252, zinc binds directly to the surface hydroxyl groups of the white filler, without the interposition of any group or spacer, with bonds of the type Zn-O-Si, detectable for example by Si <29> -NMR analysis. In the present description, this direct bond will also be referred to as the "anchor" of the zinc to the white filler.

In the present description, the term "zinc compound" indicates a compound selected from ZnO, Zn (OH) 2, and the organic or inorganic salts of Zn <2+>.

In the present description, the term "elastomeric compound" indicates the product obtained by mixing and, optionally, heating of at least one elastomeric polymer with at least one of the additives commonly used in the preparation of compounds for tires.

In the present description, the term "non-vulcanizable elastomeric blend" indicates the product obtained by mixing at least one elastomeric polymer with at least one of the additives commonly used in the preparation of rubber compounds, with the exception of vulcanizing agents. A non-vulcanizable elastomeric blend may also be referred to as phase (1) elastomeric blend. In the present description, the term "vulcanizable elastomeric blend" indicates an elastomeric blend ready for vulcanization, in which all the additives including the vulcanization ones have been incorporated. A vulcanizable elastomeric blend may also be referred to as phase (2) elastomeric blend.

In the present description, the term "vulcanized elastomeric blend" indicates the material obtained by vulcanization of a vulcanizable elastomeric blend. In the present description, the term "classical process" referring to the compound preparation process indicates a multiphase preparation process in which the compatibilizing agent (silane) is fed before the reaction between the fatty acid and zinc. In a classic process, therefore, the compatibilizing agent is added at an earlier or simultaneous stage, with respect to the addition of fatty acid and / or zinc. In the present description, the term "process according to the invention" referring to the preparation process of the elastomeric compounds, indicates a multiphase preparation process in which the compatibilizing agent (E) (silane) is introduced into the mixer only after it has been completed. the addition and processing of the fatty acid (C) and of the compound (D) comprising zinc directly bound to a white filler.

In the process according to the invention, the processing of the fatty acid (C) and the compound (D) comprising zinc directly linked to a white filler is continued at least for the time necessary for the substantial completion of the reaction between fatty acid and zinc.

In the present description, the term "mixing phase (1)" indicates the phase of the production process of the elastomeric compound in which one or more additives can be incorporated by mixing and possibly heating, except for the vulcanization ones which are fed in phase (2 ).

This phase may include several intermediate processes during which one or more of the additives are incorporated, except for the vulcanization ones, followed by further processing.

This phase may include a "chewing phase" here also referred to as "phase 1-0" that is an initial phase during which the one or more diene elastomeric polymers (A) are mechanically processed, possibly hot and possibly with the addition of one or more additives, generally excluding the vulcanization ones and the compatibilizing agent (E), in order to form and make the elastomeric mass more workable and homogeneous. In this phase, the polymer is generally processed, possibly with plasticizers, lowering its viscosity and increasing its exposed surface, thus making it easier to incorporate additives, especially fillers.

In the present description, the term "mixing phase (2)" indicates the subsequent phase of the production process of the elastomeric blend in which the vulcanizers and, preferably, the vulcanization accelerators and / or retardants are introduced and mixed into the material, at a temperature controlled, generally at a mixing temperature below 160 ° C.

The mixing phase (1) is also called the “non-productive phase” as the components of the mixture are fed to the mixing device except the crosslinking ones (for example, sulfur and accelerators).

The mixing phase (2) is instead called the production phase. In this phase, the elastomeric blend obtained from step (1) and the vulcanization additives, capable of favoring and / or controlling crosslinking, are fed to the mixing device, so as to provide the vulcanizable elastomeric blend.

In the present description, the term "batch or batch mixer" indicates a mixing device suitable to be periodically fed with the components of the elastomeric composition in predefined quantities (batches) and to mix them for a predetermined time in order to obtain the elastomeric composition. At the end of the mixing phase, the elastomeric composition obtained is completely discharged from the mixing device in a single solution.

Typically, a discontinuous mixer comprises a pair of tangential or interpenetrating rotors housed in a mixing chamber and rotating in the opposite direction, so as to mix the components introduced into the mixing chamber from its top.

For this purpose, the discontinuous mixer can be equipped with a pneumatic or hydraulic cylinder positioned in the upper part of the mixing chamber and a piston that moves both upwards to open the mixing chamber, allowing the introduction of the ingredients of the mixing chamber. composition by special loading hoppers, both downwards to exert a pressure on the material being processed in the mixing chamber and located above the pair of rotors.

A pneumatic or hydraulic system positioned at the bottom of the mixing chamber allows the elastomeric composition to be discharged at the end of the mixing cycle through the opening of a special mouth.

Specific examples of batch mixers which can be advantageously used according to the present invention are of the closed type (Banbury®, Intermix®, Tandem Mixer HF) or open (open mill or Z-blade).

In the present description, the term "continuous mixer" indicates a mixing device suitable for receiving in continuous feed the ingredients of an elastomeric composition, for mixing and / or reprocessing them in order to produce and discharge an elastomeric composition in a continuous flow (except for possible stops of the mixing device due to maintenance, or change of the elastomeric composition recipe), in contrast to the periodic loading / unloading of the batch mixing device.

The continuous mixer is capable of substantially mixing the ingredients of an elastomeric composition, especially in cold feeding / dosing conditions, and chewing the elastomeric material by raising its temperature so as to make it workable and plastic to facilitate incorporation and / or distribution of ingredients within the polymer matrix. The continuous mixer is therefore mainly equipped with mixing portions capable of giving the composition a high shear stress, and with any redistribution portions. The continuous mixer is also equipped with transport portions capable of transporting the composition being processed from one longitudinal end of the internal chamber to the other. Examples of continuous mixing devices are continuous mixing devices of the twin-screw (in English 'twin-screw') or multi-screw (for example ring mixers), interpenetrating and co-rotating, or planetary type devices.

The term 'planetary mixer' means a continuous mixing device having a central rotor and a plurality of mixing satellites each of which, driven by the central rotor, rotates simultaneously around its own axis and around the central rotor.

Both the batch mixer and the continuous mixer are able to supply the elastomeric composition with sufficient energy to mix and disperse the charge in the elastomeric polymer even in the case of cold feeding, unlike other handling devices of elastomeric composition, such as conveyor devices. and devices for fabricating a semi-finished element.

In the present description the term "raw or raw" is generally used to indicate a material, compound, composition, component or tire which has not yet been cured.

DETAILED DESCRIPTION OF THE INVENTION

The process for the preparation of a vulcanizable elastomeric compound for tires according to the invention will be illustrated in detail below.

This process is characterized by one or more of the following preferred aspects taken alone or in combination with each other, in particular by the use of at least one activating filler (D) and by the sequence of adding some components,

The present process may be a continuous process but, preferably, it is a batch process.

The present process, when discontinuous, can be carried out in one or more mixers, preferably in a single mixer.

The process according to the invention comprises a mixing step (step 1) of at least one diene elastomeric polymer (A) and at least one additive for elastomeric compounds, which is not a vulcanizing agent (B).

The at least one additive for elastomeric blends that is mixed together with the at least one diene elastomeric polymer (A) in the mixing step (1) can be for example a fatty acid (C), a compound (D) comprising zinc directly bound to a white filler, optionally a compatibilizing agent (E), a reinforcing filler (H), an antioxidant (I), a wax (L), a plasticizer (M) and the like.

Generally in the mixing step (1) no vulcanizing agent (B) and, preferably, neither accelerating agents (F) or retardants (G) the vulcanization are added.

In one embodiment, the process according to the invention comprises a mixing step (step 1) of at least one diene elastomeric polymer (A), of at least one fatty acid (C), of at least one compound (D) comprising zinc directly bound to a white filler and, only after their addition and processing, of at least one compatibilizing agent (E).

In one embodiment, the process according to the invention comprises a mixing step (step 1) of at least one diene elastomeric polymer (A), of at least one fatty acid (C) and of at least one compound (D) comprising zinc directly bound to a white charge. In this variant of the process, the at least one compound (D) comprising zinc directly bound to a white filler and the at least one fatty acid (C) are processed in phase (1) while the at least one compatibilizing agent (E) is powered in phase (2).

In one embodiment, the process according to the invention comprises a mixing step (step 1) of at least one diene elastomeric polymer (A), of at least one fatty acid (C) or of at least one compound (D) comprising zinc directly bound to a white charge. In this variant of the process, the at least one compound (D) comprising zinc directly bound to a white filler or the at least one fatty acid (C) respectively can be added and processed in phase (2), followed by the addition of the at least one compatibilizing agent (E).

The mixing phase (1) of the present process can comprise several intermediate processing phases, indicated here as phase 1-0, 1-1, 1-2, 1-3 etc., distinguishable by the momentary interruption of the mixing and by the addition of one or more ingredients but without intermediate discharge of the mixture.

Preferably, in the case of a discontinuous process in which the mixing phase (1) includes several intermediate stages of processing, the intermediate compounds are not unloaded but reworked, with the addition of the appropriate additives, in the same mixer.

The mixing phase (1) preferably comprises an initial chewing phase (phase 1-0) during which the at least one elastomeric polymer (A) is processed. In chewing, the polymer is subjected to mechanical and, preferably, thermal processing to reduce its viscosity, increase its exposed surface and workability, making it easier to incorporate additives. Furthermore, in the case of mixtures of several polymers (A), chewing ensures a better homogeneity of the mixture.

Optionally, the at least one fatty acid (C) and / or the at least one compound (D) comprising zinc directly bound to a white filler or other additives of phase 1 can be incorporated in the chewing but preferably not the compatibilizing agent (E) .

In the present process the at least one fatty acid (C) can be fed, in whole or in part, in the mixing phase (1).

Preferably the fatty acid (C) is all fed into the mixing phase (1).

Eventually, the fatty acid (C) can be fed in whole or in part in the chewing phase (phase 1-0) if present.

Alternatively, the addition of the fatty acid (C) can also be divided into several intermediate phases of the mixing phase (1), as long as they precede the phase of adding the compatibilizing agent (E).

In the present process, in the mixing step (1) at least one compound (D) comprising zinc directly bound to a white filler can be fed, in whole or in part.

Preferably, the compound (D) comprising zinc directly bound to a white filler is all fed in phase (1).

Optionally, the compound (D) comprising zinc directly bound to a white filler can be fed in whole or in part in the chewing phase (phase 1-0) if present.

Alternatively, the addition of the compound (D) comprising zinc directly linked to a white filler can also be divided into several intermediate phases of the mixing phase (1), provided they precede the phase of adding the compatibilizing agent (E).

Preferably, the compound (D) comprising zinc directly bound to a white filler is not fed into the chewing step (step 1-0), if present.

In the present process in the mixing step (1), if present, other additives can optionally be fed in addition to the at least one fatty acid (C), the at least one compound (D) comprising zinc directly bound to a white filler and, the at least one compatibilizing agent (E), such as for example oils and waxes.

In the present process, the optional chewing phase (phase 1-0) can be carried out in a batch mixer or in a continuous mixer as defined above, for times for example between 30 seconds to 2 minutes, at mixing temperatures typically from 70 ° C to 155 ° C.

In the mixing step (1) at least one elastomeric polymer (A) and optionally at least one fatty acid (C) and / or at least one compound (D) comprising zinc directly linked to a white filler and optionally, if both the acid fat (C) and the compound (D) comprising zinc directly bound to a white filler were fed in this step, at least one compatibilizing agent (E), provided that the compatibilizing agent (E) if present in this step, is subsequently added to the feeding and processing of the fatty acid (C) and of the compound (D) comprising zinc directly bound to a white filler.

Preferably, the at least one fatty acid (C), the at least one compound (D) comprising zinc directly bound to a white filler and the at least one compatibilizing agent (E) are all fed in phase (1), again in a manner that the compatibilizing agent (E) is added subsequently to the feeding and processing of the fatty acid (C) and of the compound (D) comprising zinc directly bound to a white filler.

The addition of the at least one compatibilizing agent (E) can take place in one or more of the possible intermediate steps of the mixing step (1), preferably not in the 1-0 chewing step or, alternatively, in whole or in part, in step (2), again on condition that the reaction between the at least one fatty acid (C) and the at least one compound (D) comprising zinc directly bound to a white filler, is substantially completed before the addition of the agent compatibilizer (E). Typically the processing step of the at least one fatty acid (C) and of the at least one compound (D) comprising zinc directly bound to a white filler, during which the reaction between the fatty acid and the zinc takes place, is continued for at least 30 seconds or more at a mixing temperature preferably at least equal to, more preferably higher than, the melting temperature of the fatty acid, typically at a mixing temperature of at least 70 ° C. For example, processing can be continued for at least 90 seconds and at a mixing temperature of at least 100 ° C, before adding the compatibilizing agent (E). The expert in the field can appropriately modify the processing time and temperature depending, for example, on the type of mixer, the mass being processed, the type of polymer, the type of fatty acid and its melting temperature.

In step (1), mixing is carried out at mixing temperatures generally comprised between 70 and 160 ° C and for times typically between 2 and 20 minutes. In the case of two or more intermediate phases, the expert in the sector is able to decide the optimal operating conditions for each of them, taking into consideration the type and intended use of the mixture, the type of mixer, the components to be working in each intermediate step and the need to substantially complete the reaction between the fatty acid (C) and the compound (D) comprising zinc directly bound to a white filler before the subsequent addition of the compatibilizing agent (E).

Indicatively, each intermediate phase of phase (1) is generally prolonged for a time varying from 2 to 10 minutes and carried out at mixing temperatures between 70 and 160 ° C.

In phase (1) of the present process, the order of addition of the components of the mixture can always vary provided that any compatibilizing agent (E) is fed not before the substantial completion of the reaction between the fatty acid (C) and the compound (D) comprising zinc directly bonded to a white filler.

At the end of phase (1), the elastomeric mixture is fed, to the same or to a different mixer, for the phase of incorporation of the vulcanization agents (phase 2)

Before proceeding with step (2), it may be advantageous to carry out an unloading and / or resting step of the non-vulcanizable elastomeric blend in order to allow the completion of any reactions.

Preferably, the mixture of phase (1) is discharged before proceeding with phase (2).

In the subsequent step (2), at least one vulcanizing agent (B) is incorporated. Optionally, in step (2) at least one vulcanization accelerator (F), at least one vulcanization retardant agent (G) can be added, and if not already fed completely in the mixing step (1), the at least one fatty acid (C) and / or the at least one zinc compound anchored on a white filler (D) and upon completion of their addition and processing, the at least one compatibilizing agent (E).

The mixing phase (2) of the present process can comprise several intermediate processing phases, indicated as phase 2-0, 2-1, 2-2, etc., characterized by the momentary interruption of mixing to allow the addition of one or more ingredients but without intermediate discharge of the mixture.

In the process of preparing elastomeric compounds according to the invention, if the compatibilizer (E) is fed in more than one step, the addition of the at least one fatty acid (C) and the at least one compound (D) comprising zinc directly bound to a white filler must take place in one or more phases preceding the first feeding phase of the compatibilizing agent (E).

In step (2) of the present process, the mixing temperature is generally kept below 160 ° C, preferably at 140 ° C, more preferably at 120 ° C, so as to avoid any unwanted pre-crosslinking phenomenon.

Generally in step (2) the mixing can be carried out at mixing temperatures between 70 and 155 ° C and for times between 2 and 10 minutes.

At the end of step (2), the present process provides for a step of unloading the vulcanizable elastomeric compound which will be destined to the subsequent typical processing steps for the production of tires and their components.

In one or more of the steps of the present process, other additives commonly used in the production of tire compounds can be added, selected on the basis of the specific application for which the composition is intended. For example, anti-aging agents, plasticizers, adhesives, anti-ozone agents, modifying resins or their mixtures can be added.

In the present process, the at least one diene elastomeric polymer (A) can be selected from those commonly used in sulfur curable elastomeric compositions, which are particularly suitable for producing tires, i.e., among elastomeric polymers or copolymers with an unsaturated chain having a glass transition temperature (Tg) generally lower than 20 ° C, preferably made up in the range from 0 ° C to -110 ° C.

Preferably, the diene elastomeric polymer has a weight average molecular weight (M ̅w) higher than 80000 g / mol.

These polymers or copolymers can be of natural origin or can be obtained by solution polymerization, emulsion polymerization or gas phase polymerization of one or more conjugated diolefins, optionally mixed with at least one comonomer selected from monovinylarenes and / or polar comonomers in a quantity not more than 60% by weight.

The conjugated diolefins generally contain from 4 to 12, preferably from 4 to 8 carbon atoms and can be selected, for example from the group comprising: 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1, 3-pentadiene, 1,3-hexadiene, 3-butyl-1,3-octadiene, 2-phenyl-1,3-butadiene and their mixtures.

1,3-butadiene and isoprene are particularly preferred.

Monovinylarenes, which can optionally be used as comonomers, generally contain from 8 to 20, preferably from 8 to 12 carbon atoms and can be selected, for example, from: styrene; 1-vinyl naphthalene; 2-vinyl naphthalene; various alkyl, cycloalkyl, aryl, alkylaryl or arylalkyl derivatives of styrene such as, for example, α-methylstyrene, 3-methylstyrene, 4-propylstyrene, 4-cyclohexylstyrene, 4dodecylstyrene, 2-ethyl-4-benzylstyrene, 4-p-tolylstyrene, 4- (4-phenylbutyl) styrene, and their mixtures. Styrene is particularly preferred.

Polar comonomers, which can optionally be used, can be selected, for example from: vinylpyridine, vinylquinoline, esters of acrylic and alkylacrylic acids, nitriles, or their mixtures, such as, for example, methyl acrylate, ethyl acrylate , methyl methacrylate, ethyl methacrylate, acrylonitrile and their mixtures.

Preferably, the diene elastomeric polymer (A) which can be used in the present invention can be selected, for example, from: cis-1,4-polyisoprene (natural or synthetic, preferably natural rubber), 3,4-polyisoprene, polybutadiene ( in particular polybutadiene with a high content of 1,4-cis), possibly halogenated isoprene / isobutene copolymers, 1,3-butadiene / acrylonitrile copolymers, styrene / 1,3-butadiene copolymers, styrene / isoprene / 1 copolymers , 3-butadiene, styrene / 1,3-butadiene / acrylonitrile copolymers, and mixtures thereof.

The aforementioned vulcanizable elastomeric blend may optionally comprise an elastomeric polymer of one or more monoolefins with an olefin comonomer or their derivatives (A '). The monoolefins can be selected from: ethylene and α-olefins generally containing from 3 to 12 carbon atoms, such as, for example, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and their mixtures. The following are preferred: copolymers between ethylene and an α-olefin, optionally with a diene; homopolymers of isobutene or their copolymers with small quantities of a diene, which are optionally at least partly halogenated. The diene optionally present generally contains from 4 to 20 carbon atoms and is preferably selected from: 1,3-butadiene, isoprene, 1,4-hexadiene, 1,4-cyclohexadiene, 5-ethylidene-2-norbornene, 5- methylene-2-norbornene, vinylnorbornene and their mixtures. Among them, the following are particularly preferred: ethylene / propylene copolymers (EPR) or ethylene / propylene / diene copolymers (EPDM); polyisobutene; butyl rubbers; halobutyl rubbers, in particular chlorobutyl or bromobutyl rubbers; or their mixtures. A diene elastomeric polymer (A) or an elastomeric polymer (A ') functionalized by reaction with terminating agents or suitable coupling agents can also be used. In particular, diene elastomeric polymers obtained by anionic polymerization in the presence of an organometallic initiator (in particular an organolithium initiator) can be functionalized by reacting the residual organometallic groups derived from the initiator with suitable terminating agents or coupling agents such as, for example, imines, carbodiimides, alkyl tin halides, substituted benzophenones, alkoxysilanes or aryloxysilanes.

In the present process for the preparation of the vulcanizable elastomeric blend, the at least one elastomeric polymer (A) can comprise one or more diene elastomeric polymers (A) as defined above in mixture which can be advantageously subjected to the chewing step (step 1-0) to be better blended.

In the present process, the amount used of the at least one elastomeric polymer (A) or of the mixture of two or more elastomeric polymers (A) as defined above amounts to a total of 100 phr.

In the present process, the at least one vulcanizing agent (B) is preferably selected from sulfur, or alternatively, sulfur-containing molecules (sulfur donors), such as, for example, caprolactam disulfide (CLD), bis [(trialkoxysilyl) propyl] polysulfides , dithiophosphates, phosphoryl polysulfide (SDT) and their mixtures.

Preferably the vulcanizing agent (B) is sulfur, preferably chosen from soluble sulfur (crystalline sulfur), insoluble sulfur (polymeric sulfur) and sulfur dispersed in oil and their mixtures.

Commercial examples of suitable vulcanizing agents (B) are 65% sulfur known as Lanxess' Rhenogran, 67% sulfur known as Eastman's Crystex OT33, 95% sulfur known as Eastman's of SchwefelKC of Solvay, the sulfur with a rhombic crystalline structure known by the trade name of Sulfur (1% oil and 0.3% silica) of Zolfindustria, The vulcanizing agent (B) can be present in the vulcanizable elastomeric compound in an overall quantity generally from 0.1 to 15 phr, preferably 0.5 to 10 phr, even more preferably 1 to 7 phr.

The present elastomeric blend can comprise one or more vulcanizing agents (B) as defined above in blend.

In the present process, the vulcanizing agent (B) is preferably used together with adjuvants such as accelerators and / or retarders of vulcanization known to those skilled in the art.

In the present process, the fatty acid (C) is preferably selected from the saturated or unsaturated fatty acids containing from 8 to 26 carbon atoms, their esters, their salts and their mixtures.

Preferred fatty acids are ac. lauric (C12), myristic acid (C14), ac. palmitic acid (C16), stearic acid (C18), ac. behenic (C22), the ac. lignocerico (C24).

Examples of mixtures of fatty acids are the mixture C18 / C16 (Ac. Stearico and Ac. Palmitico), C12 / C14 (Ac. Laurico and Ac. Miristico), C22 / C24 (Ac. Beenico and Ac. Lignocerico).

Preferably the fatty acid (C) is stearic acid or an ester or salt thereof, more preferably it is stearic acid.

In the present process of preparing the vulcanizable elastomeric blend the overall quantity of fatty acid (C) is generally comprised between 0.05 and 20 phr, preferably between 0.1 and 15 phr, more preferably between 0.5 and 5 phr.

The compound (D) comprising zinc directly bonded to a white filler or activating filler (D) is a preferably inorganic compound comprising a zinc compound, preferably zinc oxide or zinc hydroxide, wherein the zinc is bonded directly to the surface of a white charge.

The zinc present in compound (D) is in the form, for example, of zinc oxide, zinc hydroxide, divalent zinc salt, such as zinc acetate or a zinc silicate or their mixtures, and not metallic zinc (Zn °). Zinc is preferably present as zinc oxide.

Preferably the compound (D) comprising zinc directly bonded to a white filler comprises zinc oxide anchored on silica.

Preferably, the zinc oxide anchored on the white filler is a zinc oxide in particles of average size between 3 nm and 100 nm, preferably between 4 and 10 nm (nanoparticles).

The zinc oxide nanoparticles can be amorphous or crystalline, and of various morphology, for example spherical, tetragonal, orthorhombic, monocline or tricline. Preferably the zinc oxide nanoparticles are amorphous.

The zinc content in the compound (D) comprising zinc directly bound to a white filler can generally vary from 0.5 to 50% by weight, preferably from 1 to 25%, more preferably from 7 to 14% by weight with respect to the total weight of compound (D).

The zinc content can be determined for example with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) mass spectrometry as reported in the experimental part.

The compound (D) comprising zinc directly bonded to a white filler preferably has a zinc oxide content from 1 to 65%, preferably from 5 to 30%, more preferably from 7 to 15% by weight with respect to the total weight of the compound ( D).

The white filler to which the zinc binds can be any conventional white reinforcing filler that has hydroxyl groups on the surface.

The white filler is preferably selected from silica and conventional silicates, in the form of fibers, lamellae or granules, such as for example bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, paligorskite also known as attapulgite, montmorillonite, alloysite and the like, possibly modified by acid treatment and / or derivatized, and their mixtures, more preferably is silica.

The silica on which the zinc compound is anchored can vary in shape, specific surface area and size.

Examples of silica are pyrogenic silica, precipitated amorphous silica, wet silica (hydrated silicic acid), or mixtures thereof.

Examples of suitable commercial silicas are the precipitated silica Rhodia Zeosil MP1165 (BET specific surface area 160 m <2> / g), Ultrasil VN3 GR (BET specific surface area 180 m <2> / g) and Zeosil 1115 MP (BET surface area specification 95-120 m <2> / g). Preferably the silica has a specific surface area (BET) of at least 120 m <2> / g, more preferably of at least 140 m <2> / g.

Preferably the silica has a specific surface area (BET) lower than 220 m <2> / g, more preferably lower than or equal to 180 m <2> / g

Figure 2 shows the TEM image - taken from Chemical Engineering Journal 275 (2015) 245–252 - of an activating filler suitable for use in the present process comprising zinc oxide nanoparticles anchored on silica.

The compound (D) comprising zinc directly bound to a white filler can be prepared and characterized according to known methods, for example as described in the Chem articles. Eng. 275 (2015), 245 - 252 or in Solid State Phenom. 151 (2009) 264-268 or as reported in this experimental part.

In the present process of preparing the vulcanizable elastomeric blend, the total amount of compound (D), comprising zinc directly bound to a white filler, in the elastomeric blend is between 1 and 100 phr, preferably between 5 and 80 phr, more preferably between 10 and 30 phr.

In the present process, at least one compatibilizing agent (E) is added. The term "compatibilizing agent (E)" generally refers to a compound capable of interacting with a reinforcing filler, in particular a white filler such as silica, and of binding it to the diene elastomeric polymer during vulcanization.

In the present process, the compatibilizing agent (E) is generally a silane chosen from those having at least one hydrolyzable group, which can be identified, for example, by the following general formula (I):

(R) 3Si-CnH2n-X (I) where the R groups, which may be identical or different, are selected from alkyl, alkoxy or aryloxy or halogen groups, provided that at least one of the R groups is an alkoxy or aryloxy group or a halogen; n is an integer from 1 to 6 inclusive; X is a group chosen from: nitrous, mercapto, amino, epoxide, vinyl, imide, chlorine, - (S) mCnH2n-Si- (R) 3 and -S-COR, where m and n are integers from 1 to 6 inclusive and i R groups are defined as above.

Preferred compatibilizing agents (E) are bis (3-triethoxysilylpropyl) tetrasulfide (TESPT) and bis (3-triethoxysilylpropyl) disulfide (TESPD).

A commercial example of suitable compatibilizing agent (E) is TESPT or bis (3-triethoxysylpropyl) tetrasulfide Si69 marketed by Evonik.

Preferably, the compatibilizing agent (E) is introduced into the elastomeric blend in a total amount of between 0.1 phr and 20 phr, preferably between 0.5 phr and 10 phr.

The present elastomeric blend can comprise one or more compatibilizing agents (E) as defined above in the blend.

In the present process the vulcanization accelerator agent (F) is preferably selected from dithiocarbamates, guanidines, thioureas, thiazoles, sulfenamides, sulfenimides, thiurams, amines, xanthates and their mixtures.

Preferably the accelerating agent (F) is selected from N-cyclohexyl-2-benzothiazolsulfenamide (CBS), N-tert-butyl-2-benotiazol-sulfenamide (TBBS) and their mixtures.

A commercial example of a suitable accelerating agent (F) is N-cyclohexyl-2-benzothiazyl-sulfenamide Vulkacit® (CBS or CZ) marketed by Lanxess. The accelerating agent (F) can be present in the vulcanizable elastomeric compound in a total amount generally between 0.05 phr and 10 phr, preferably between 0.1 phr and 5 phr.

The present elastomeric blend can comprise one or more accelerating agents (F) as defined above in blend.

In the present process, the vulcanization retardant agent (G) can be chosen for example from urea, phthalic anhydride, N-nitrosodiphenylamine, N-cyclohexylthiophthalimide (CTP or PVI), and their mixtures.

A commercial example of a suitable retarding agent (G) is Lanxess N-cyclohexylthiophthalimide VULKALENT G.

The retarding agent (G) can be present in the vulcanizable elastomeric blend in an amount generally between 0.05 phr and 2 phr.

The present elastomeric blend can comprise one or more retarding agents (G) as defined above in blend.

Preferably in the present process, preferably in the mixing step (1), one or more optional additives can be fed such as for example at least one reinforcing filler (H), at least one antioxidant agent (I), at least one wax (L) and at least a plasticizer (M).

In the present process with reinforcing filler (H) is meant a conventional filler, which has not anchored the zinc compound to the surface.

In the present process the reinforcing filler (H) is selected from carbon black, conventional silica, such as silica from sand precipitated with strong acids, preferably amorphous, hydrotalcite, diatomaceous earth, calcium carbonate, titanium dioxide, talc, alumina , aluminosilicates, kaolin, silicate fibers and their mixtures.

Preferably the reinforcing filler (H) is selected from carbon black, conventional silica, silicate fibers and their mixtures, preferably it is silica.

Carbon black can be chosen from among those of standard grade for tires, i.e. having a surface area of not less than 20 m <2> / g, more preferably greater than 50 m <2> / g (measured in accordance with the ASTM standard D6556-16).

A commercial example of a suitable filler (H) is Zeosil 1165MP silica from Solvay Rhodia.

Commercial examples of carbon black are N375 or N234 marketed by Birla Group (India) or Cabot Corporation.

The reinforcing filler (H) can be present in the vulcanizable elastomeric blend in an amount generally comprised between 0 phr and 120 phr, preferably between 3 phr and 80 phr.

In one embodiment, the reinforcing filler (H) may be absent, in which case the reinforcing function is performed by the compound (D).

For some applications, the elastomeric blend prepared according to the present process can comprise at least 1 phr, more preferably at least 2 phr, more preferably at least 3 or 4 phr of carbon black, which advantageously protects the elastomer from aging caused by the action of ultraviolet radiation.

The present elastomeric blend can comprise one or more reinforcing fillers (H) as defined above in blend.

In the present process as antioxidant (I), phenylenediamine, diphenylamine, dihydroquinoline, phenol, benzimidazole, hydroquinone and their derivatives, optionally in mixture, can be used.

In the present process the antioxidant agent (I) is preferably selected from N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N- (1,3-dimethyl-butyl) -N'-phenyl-pphenylenediamine (6PPD ), N, N'-bis- (1,4-dimethyl-pentyl) -p-phenylenediamine (77PD), N, N'-bis- (1-ethyl-3-methylpentyl) -p-phenylene-diamine (DOPD ), N, N'-Bis- (1,4-dimethylpentyl) -p-phenylenediamine, N, N'-diphenyl-p-phenylenediamine (DPPD), N, N'-ditolyl-p-phenylenediamine (DTPD), N , N'-di-beta-naphthyl-p-phenylenediamine (DNPD), N, N'-Bis (1-methylheptyl) -p-phenylenediamine, N, N'-Di-sec-butyl-p-phenylenediamine (44PD) , N-phenyl-N'-cyclohexyl-p-phenylenediamine, N-phenyl-N'-1-methylheptyl-pphenylenediamine and the like, and their mixtures, preferably N- (1,3-dimethyl-butyl) -N'- phenyl-p-phenylenediamine (6-PPD).

A commercial example of a suitable antioxidant agent (I) is Solutia / Eastman's 6PPD.

The antioxidant agent (I) can be present in the vulcanizable elastomeric blend in a total amount generally between 0 phr and 20 phr, preferably between 0.5 phr and 10 phr.

In the present process the wax (L) can be for example a petroleum wax or a mixture of paraffins.

Commercial examples of suitable waxes are Repsol's N-paraffin blend and Rhein Chemie's Antilux® 654 microcrystalline wax.

The wax (L) can be present in the vulcanizable elastomeric blend in an overall quantity generally comprised between 0 phr and 20 phr, preferably between 0.5 phr and 5 phr.

In the present process, in order to further improve workability, at least one plasticizing agent (M) can be added to the elastomeric compound, generally selected from mineral oils, vegetable oils, synthetic oils, low molecular weight polymers and their mixtures, such as, for example for example, aromatic oil, naphthenic oil, phthalates, soybean oil and their mixtures. The quantity of plasticizer is generally comprised between 0 phr and 70 phr, preferably between 5 phr and 30 phr. Preferably, the plasticizing agent (M) is added in the chewing step of the polymer 1-0, if present.

By way of non-limiting example, some embodiments of the present process are reported below.

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A);

phase 1-1: ac. fat (C);

phase 1-2: activating charge (D);

phase 1-3: compatibilizer (E);

phase 2: vulcanizer (B).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A);

phase 1-1: ac. fat (C);

phase 1-2: activating charge (D);

phase 1-3: compatibilizer (E);

phase 2: vulcanizer (B) and compatibilizer (E).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A) and ac. fat (C);

phase 1-1: ac. fat (C) and activating filler (D);

phase 1-2: compatibilizer (E);

phase 2: vulcanizer (B).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A) and ac. fat (C);

phase 1-1: activating charge (D);

phase 1-2: compatibilizer (E);

phase 2: vulcanizer (B).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A);

phase 1-1: charge (H), ac. fat (C) and antioxidant (I);

phase 1-2: activating charge (D);

phase 1-3: compatibilizer (E);

phase 2: vulcanizer (B) and accelerator (F).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A);

phase 1-1: charge (H), ac. fat (C) and antioxidant (I);

phase 1-2: activating charge (D);

phase 1-3: compatibilizer (E);

phase 2: vulcanizer (B), accelerator (F) and compatibilizer (E).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A) and ac. fat (C);

phase 1-1: charge (H), ac. fat (C) and activating filler (D);

phase 1-2: antioxidant (I), wax (L) and compatibilizer (E);

phase 2: vulcanizer (B), accelerator (F) and retardant (G).

In an implementation of this process, the order of addition of the components of the mixture is as follows:

phase 1-0: polymer (A) and ac. fat (C);

phase 1-1: charge (H) and activating charge (D);

phase 1-2: antioxidant (I), wax (L) and compatibilizer (E);

phase 2: vulcanizer (B), accelerator (F) and retardant (G).

A second aspect of the present invention is represented by a vulcanizable elastomeric blend obtained according to the process described above.

Preferably, the vulcanizable elastomeric blend according to the invention comprises zinc in an amount lower than 4 phr, more preferably lower than 3 phr, even more preferably lower than 2 phr with consequent advantage for the environment of a lower release of the same compared to conventional elastomeric compounds. . Preferably the vulcanized elastomeric blend according to the invention comprises zinc in an amount lower than 4 phr, more preferably lower than 3 phr, even more preferably lower than 2 phr.

In the elastomeric blend according to the invention, zinc is generally present in various forms, for example in ionic form such as Zn <2+>, covalently linked and / or complexed but not in the form of metallic zinc (Zn °).

The amount of zinc in the blend can be determined for example by X-ray fluorescence (XRF), as described in the experimental part.

The present vulcanizable elastomeric blend can be incorporated into one or more components of the tire.

Thanks to the presence of at least one vulcanization agent (B), the vulcanizable compound can be vulcanized according to known techniques.

Thanks to the use of the compound (D) comprising zinc directly linked to a white filler as activator and to the postponed addition of the compatibilizing agent (E) according to the present process, a complete and homogeneous dispersion of the zinc is obtained with undoubted advantages in the subsequent vulcanization reaction of the elastomeric compound, such as a greater and more uniform cross-linking, the absence of unreacted zinc oxide aggregates, and in the properties of the vulcanized compound in terms of improving the load and elongation at break.

This particular reactivity is highlighted by the increase of mono- and disulfide bridges in the vulcanized compound, as measured in the present experimental part in Example 6 (Table 8) and by the reduction of the crosslinking times (see for example the T-MH values of Tables 6, 10 or T90 of Table 12) and is reflected in the trend of the normalized torque value curves shown in Figures 5 and 6.

Furthermore, the experiments reported here show that the elastomeric compound for tires prepared according to the process of the invention is characterized, at the same zinc content, by a significant reduction of the hot hysteresis (70 ° C and 100 ° C), predicting a decrease in rolling resistance in use advantageous due to the increase in tire mileage, and / or an increase in cold hysteresis (10 ° C and 23 ° C), associated with better performance of the tire in the wet.

Thanks to this process, it is possible to reduce the amount of zinc incorporated in the compounds, with important benefits for the environment, without deteriorating or even improving their performance compared to comparable conventional compounds.

According to a third aspect of the invention, the present elastomeric compound finds application in tire components such as tread, substrate, anti-abrasive strip, sidewall, sidewall insert, mini-sidewall, underliner, rubber layers, bead filling and foil, more preferably in the tread , in the substrate and in the side.

Preferably the tire component according to the invention consists of the vulcanizable compound according to the invention (raw component) or the vulcanized compound obtained by its vulcanization (vulcanized component).

A fourth aspect of the present invention is represented by a tire for vehicle wheels comprising at least one of the components indicated above.

Preferably, the tire for vehicle wheels of the invention comprises at least one tire component consisting of a vulcanizable elastomeric blend (raw component) in accordance with the second aspect of the invention or of a vulcanized elastomeric blend obtained by its vulcanization. In one embodiment, a vehicle tire according to the present invention comprises at least

- a carcass structure comprising at least one carcass layer having opposite lateral edges associated with respective bead structures;

- optionally a pair of sidewalls respectively applied on the lateral surfaces of the carcass structure in an axially external position;

- optionally a belt structure applied in a radially external position to the carcass structure;

- a tread band applied in a radially external position to said carcass structure or, if present, belt structure,

- possibly a layer of elastomeric material, said substrate, applied in a radially internal position with respect to said tread band,

in which at least one component selected from said pair of sidewalls, said substrate and said tread band comprises the, or preferably consists of, the elastomeric compound according to the invention.

An embodiment according to the present invention relates to a tire for high-performance vehicles (HP, SUV and UHP) in which at least one component, preferably selected from the substrate, sidewall and tread band, comprises, or preferably consists of, the elastomeric compound according to the invention.

An embodiment according to the present invention relates to a tire for heavy vehicles in which at least one component, preferably selected from the substrate, sidewall and tread band, comprises, or preferably consists of, the elastomeric compound according to the invention.

The tire according to the invention can be a tire for two or four-wheeled vehicles.

In one embodiment, the tire according to the invention is a tire for bicycle wheels.

A tire for bicycle wheels typically comprises a carcass structure turned up around a pair of bead cores at the beads and a tread band arranged in a position radially external to the carcass structure.

The carcass structure is designed to withstand the inflation pressure and to withstand the weight of the bicycle and cyclist. It comprises one or more carcass plies, each comprising a plurality of suitably oriented reinforcement cords. In the case of several carcass plies, they are inclined relative to each other to form a crossed structure.

The bead cores have the task of ensuring the anchoring of the tire to the wheel rim.

An air chamber can be provided in a radially internal position to the carcass structure into which pressurized air is introduced.

The tire according to the invention can be for summer or winter use or for all seasons.

The tire according to the present invention can be manufactured according to a process which includes:

- forming components of a green tire on at least one forming drum; - shaping, molding and vulcanizing the tire;

in which forming at least one of the green tire components comprises:

- making at least one raw component comprising the, or preferably consisting of, the vulcanizable elastomeric blend of the invention.

DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates in radial half-section a tire for vehicle wheels, comprising at least one component formed by an elastomeric compound prepared according to the process of the invention.

Figure 1 illustrates in radial half-section a tire for vehicle wheels according to the invention.

In Figure 1 “a” indicates an axial direction and “X” indicates a radial direction, in particular with X-X the trace of the equatorial plane is indicated. For simplicity, Figure 1 shows only a portion of the tire, the remaining portion not shown being identical and arranged symmetrically with respect to the equatorial plane "X-X".

The tire 100 for four-wheeled vehicles comprises at least one carcass structure, comprising at least one carcass layer 101 having respectively opposite end flaps engaged with respective annular anchoring structures 102, called bead cores, possibly associated with a bead filling 104.

The carcass layer 101 is optionally made with an elastomeric compound.

The area of the tire comprising the bead core 102 and the filling 104 forms a bead structure 103 intended for anchoring the tire on a corresponding mounting rim, not shown.

The carcass structure is usually of the radial type, ie the reinforcing elements of the at least one carcass layer 101 are located on planes comprising the axis of rotation of the tire and substantially perpendicular to the equatorial plane of the tire. Said reinforcing elements generally consist of textile cords, for example rayon, nylon, polyester (for example polyethylene naphthalate PEN). Each bead structure is associated with the carcass structure by folding back the opposite side edges of the at least one carcass layer 101 around the annular anchoring structure 102 so as to form so-called carcass flaps 101a as illustrated in Figure 1.

In one embodiment, the coupling between the carcass structure and the bead structure can be provided by means of a second carcass layer (not shown in Figure 1) applied in an axially external position with respect to the first carcass layer.

An anti-abrasive strip 105 optionally made with an elastomeric compound is arranged in an external position of each bead structure 103.

Associated with the carcass structure is a belt structure 106 comprising one or more belt layers 106a, 106b placed in radial overlap with respect to each other and with respect to the carcass layer, having typically textile and / or metal reinforcement cords incorporated within a layer of vulcanized elastomeric blend.

Such reinforcing cords can have a cross orientation with respect to a circumferential development direction of the tire 100. By "circumferential" direction we mean a direction generally directed according to the direction of rotation of the tire.

In a radially outermost position to the belt layers 106a, 106b, at least one zero degree reinforcement layer 106c, commonly known as "0 ° belt", can be applied, which generally incorporates a plurality of elongated reinforcing elements, typically metal or textile cords , oriented in a substantially circumferential direction, thus forming an angle of a few degrees (for example an angle between about 0 ° and 6 °) with respect to a direction parallel to the equatorial plane of the tire, and coated with a vulcanized elastomeric compound. In a radially external position to the belt structure 106 a tread band 109 in vulcanized elastomeric compound is applied.

On the lateral surfaces of the carcass structure, each extending from one of the lateral edges of the tread 109 to the respective bead structure 103, respective sides 108 in vulcanized elastomeric blend are also applied in an axially external position.

In a radially external position, the tread band 109 has a rolling surface 109a intended to come into contact with the ground. Circumferential grooves, which are connected by transverse notches (not shown in Figure 1) so as to define a plurality of blocks of various shapes and sizes distributed on the rolling surface 109a, are generally made in this surface 109a, which for simplicity in Figure 1 it is represented smooth. An underlayer 111 in vulcanized elastomeric blend can be arranged between the belt structure 106 and the tread band 109.

A strip consisting of an elastomeric compound 110, commonly known as a "mini-flank", in a vulcanized elastomeric compound may possibly be present in the connection area between the flanks 108 and the tread band 109, this mini-flank being generally obtained by co-extrusion with the tread band 109 and allowing an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108. Preferably the end portion of the sidewall 108 directly covers the lateral edge of the tread band 109. In the case of tubeless tires, a rubber layer 112, generally known as a "liner", which provides the necessary impermeability to the tire inflation air, can also be provided in a radially internal position with respect to the carcass layer 101.

The stiffness of the tire side 108 can be improved by providing the bead structure 103 with a reinforcing layer 120 generally known as a "flipper" or additional strip-like insert.

The pinball machine 120 is a reinforcement layer which is wrapped around the respective bead core 102 and the bead filler 104 so as to at least partially surround them, said reinforcement layer being disposed between the at least one carcass layer 101 and the bead structure 103 Usually, the pinball machine is in contact with said at least one carcass layer 101 and said bead structure 103.

The pinball machine 120 typically comprises a plurality of textile cords incorporated within a layer of vulcanized elastomeric blend.

The tire bead structure 103 may comprise a further protection layer which is generally known by the term "chafer" 121 or protection strip and which has the function of increasing the rigidity and integrity of the bead structure 103.

The chafer 121 usually comprises a plurality of cords incorporated within a rubber layer of vulcanized elastomeric blend. Such cords are generally made of textile materials (for example aramid or rayon) or of metallic materials (for example steel cords).

An elastomeric blend layer or sheet can be arranged between the belt structure and the carcass structure. The layer can have a uniform thickness. Alternatively, the layer can have a variable thickness in the axial direction. For example, the layer may have a greater thickness near its axially external edges than the central (crown) zone.

Advantageously, the layer or sheet can extend over a surface substantially corresponding to the development surface of said belt structure.

In a preferred embodiment, a layer of elastomeric blend as described above, said substrate, can be placed between said belt structure and said tread band, said substrate preferably extending over a surface substantially corresponding to the development surface of said belt structure .

The elastomeric compound according to the present invention can be advantageously incorporated into one or more of the components of the tire selected from the belt structure, carcass structure, tread band, underlayer, sidewall, mini-sidewall, sidewall insert, bead, flipper, chafer, sheet and anti-abrasive strip, is preferably incorporated at least in the sides and / or in the substrate.

According to an embodiment not shown, the tire can be a tire for motorcycle wheels which is typically a tire that has a straight section characterized by a high transverse curvature.

According to an embodiment not shown, the tire can be a tire for bicycle wheels.

According to an embodiment not shown, the tire can be a tire for wheels of heavy transport vehicles, such as trucks, buses, trailers, vans, and in general for vehicles in which the tire is subjected to a high load. Preferably, such a tire is adapted to be mounted on rims having a diameter equal to or greater than 17.5 inches for directional or trailer wheels.

Figure 2 is a microscope image of a ZnO / SiO2 (D) activating charge measured with a high-resolution transmission electron microscope (HRTEM), which shows the zinc oxide particles anchored to the silica surface.

Figure 3 schematically illustrates the possible structure of the complex formed by the reaction between stearic acid and ZnO nanoparticles anchored on SiO <2>, in which Y represents a counterion such as an OH group or an acetate.

Figure 4 is an ATR-FTIR spectroscopic image showing the formation of the complex schematized in Figure 2, by reaction between stearic acid and ZnO nanoparticles anchored on SiO2 (graph a) in comparison to the classical system of ZnO and acid stearic (graph b), heated to 120 ° C for 5 minutes in a simplified model of vulcanization. In this model, low molecular weight molecules are used which mimic the reactivity of the polymer, such as the 2,3-dimethyl-2-butene used to simulate isoprene rubbers.

Figure 5 shows the normalized curve of the torque values [(Sx-Smin) / (Smax-Smin) * 100] measured over time (min.) During the vulcanization of a vulcanizable compound according to the invention and of a comparative compound ( Ex. 72 and 7.3). Figure 6 shows the normalized curve of the torque values [(Sx-Smin) / (Smax-Smin) * 100] measured over time (min.) During the vulcanization of two comparative vulcanizable compounds (Ex. 8.1 and 8.2) and of a blend according to the invention (Ex. 8.3).

Below is a description of some preparatory and comparative examples according to the invention, provided for illustrative purposes only and not as a limitation of the scope of protection.

EXPERIMENTAL PART METHODS OF ANALYSIS

The ATR-FTIR analysis was performed with a Perkin Elmer Spectrum 100 instrument (spectra with a resolution of 4 cm <-1>, region from 650 to 400 cm <-1>, 32 scans) (see Figure 4).

High Resolution Transmission Electron Microscopy (HRTEM) was performed with a 300 KV Jeol 3010 microscope with a high resolution polar pole (point-to-point resolution 0.17 nm) and equipped with a 792 slow scanning Gatan CCD camera. The powders were suspended in isopropanol and a drop of 5 µl of this suspension was deposited on a perforated carbon film supported on a 3 mm copper grid for TEM investigation (see Figure 2) Determination of the zinc content in the activating charge (D)

The content of zinc oxide anchored on a white charge (D) can be measured by ICP-AES spectrometry (Inductively Coupled Plasma-Atomic Emission Spectroscopy) with simultaneous ICP plasma spectrometer (model TJA IRIS II; excitation source: radiofrequency generator with 27.12 MHz frequency and variable output power up to 1750 W).

Determination of the zinc content in the compound by X-ray fluorescence (XRF)

The X-ray fluorescence analysis is based on the emission effect produced by a primary beam of X-rays of high intensity and appropriate energy, incident on the sample.

The sample was prepared by passing about 2 g of vulcanized mixture between the cylinders of a cold laboratory mixer until a homogeneous and compact sheet of thickness between 0.5 and 0.7 mm was obtained.

From the sheet, a circular specimen of about 4 cm in diameter was then cut into the sample holder of the instrument (X-ray dispersion wavelength fluorescence spectrometer, model ARL - XRF 8420+).

MDR rheometric analysis (according to ISO 6502): an Alpha Technologies type MDR2000 rheometer was used. The tests were performed at 170 ° C for 20 minutes, at an oscillation frequency of 1.66 Hz (100 oscillations per minute) and an oscillation amplitude of ± 0.5 °, measuring the time required to achieve a increase of two rheometric units (TS2) and the time required to reach respectively 30% (T30), 60% (T60), 90% (T90) and 100% (T-MH) of the maximum torque value ( MH). The maximum torque value MH and the minimum torque value ML were measured and their difference (MH-ML) calculated.

Properties of vulcanized materials

The elastomeric materials prepared in the previous examples were vulcanized to give specimens on which the analytical characterizations and the evaluation of the static and dynamic mechanical properties were carried out.

Unless otherwise indicated, vulcanization was carried out in a mold, in a hydraulic press at 170 ° C and at a pressure of 200 bar for a time of about 10 minutes. The hardness in IRHD degrees (23 ° C) was measured according to the ISO 48: 2007 standard, on samples of vulcanized elastomeric materials under the conditions reported in the experimental part.

Determination of the degree of total cross-linking and of the mono- and disulfide bonds (% by weight)

The measurement of the total amount of bonds or degree of total crosslinking (total number of bonds expressed as moles per gram of compound, mol / g) was performed by exploiting the swelling effect of toluene on the compound. A highly cross-linked blend will have a lower tendency to absorb solvent than a blend in which the cross-link is lower. According to this principle, an inverse relationship has been established between the amount of absorbed solvent and cross-linking. The amount of absorbed solvent was determined gravimetrically by calculating the weight difference between the swollen sample in equilibrium with the solvent and the sample itself after complete removal of the absorbed solvent, by drying under vacuum. The toluene swelling technique was also used for the determination of the quantity of mono and disulfide bonds, preceded however by a treatment with suitable reagents capable of selectively cleaving the polysulphide bonds. A mixture of piperidine and propan-2-thiol was used to cleave all poly-sulfur bonds (containing 3 or more sulfur atoms). The subsequent swelling therefore measured only the contribution of the remaining mono and di-sulfuric bonds.

The measurement of the total quantity of the bonds and the determination of the mono and disulfide bonds were carried out in parallel on two different portions of the same sample, in two different reaction vessels, according to the following procedure. A sample of vulcanized mix with dimensions 10x10x1 mm <3> (0.10 ± 0.05 g) was immersed in toluene at 25 ° C in a laboratory flask and kept in the dark for seven days. The toluene was replaced with fresh toluene after three days. On the seventh day, the swollen solid mass was weighed, then vacuum dried at 70 ° C for 12 hours and reweighed.

The volumetric fraction of the swollen rubber was calculated using this equation:

where m <0> is the weight of the compound before swelling; m <sw> the weight of the swollen compound; md is the weight of the compound dried after swelling; mso is the weight of solvent inside the swollen mass given by msw-md; ρp = 0.94 g cm <−3> is the density of the polymer; ρs = 0,87 g · cm <−3> is the density of toluene; f is the charge fraction determined by TGA. The cross-link density ν, ie the number of chains linked per gram on two different polymer chains, was evaluated in accordance with the Flory-Rehner equation [Thermodynamics of high polymer solutions, J. Chem. Phys. 10 (1942) 51–61.]

where Vs = 105.91 is the molar volume of toluene and χ is the Flory solvent-polymer interaction parameter which is 0.43 for toluene-isoprene rubber (IR).

The static mechanical properties were measured at 23 ° C according to the ISO 37: 2005 standard.

In particular, the load at 100% elongation, called CA1, the load at break CR and the elongation at break AR% were measured on samples of the elastomeric materials mentioned above.

Tensile tests were carried out on straight axis Dumbbell type specimens (ISO37 - 2011, T = 23 ° C) or on ring specimens (ISO37 - 2011, T = 23 ° C). The dynamic mechanical properties were measured according to the following methods: Dynamic modules E (traction / compression): they were measured using an Instron dynamic device in compression-traction mode according to the following procedure.

A sample of the elastomeric compounds under examination vulcanized having a cylindrical shape (length = 25 mm; diameter = 18 mm), subject to compression preload up to 25% of the longitudinal deformation with respect to the initial length and maintained at the predetermined temperature (equal to 23 ° C o 70 ° C) for the entire duration of the test, it was subjected to a sinusoidal dynamic voltage having an amplitude of ± 3.5% with respect to the length under pre-load, with a frequency of 100 Hz. The elastic properties dynamics were expressed in terms of elastic (E '), viscous (E' ') and Tan delta dynamic modulus (loss factor E' '/ E').

The Tan delta value was calculated as the ratio between the viscous dynamic modulus (E ") and the elastic dynamic modulus (E’), both being determined with the above mentioned dynamic measurements.

Dynamic G (shear) modules: were measured using a Monsanto R.P.A. 2000 according to the following method: cylindrical test samples with weights in the range from 4.5 g to 5.5 g were obtained by punching from the vulcanizable elastomeric composition of the samples and their vulcanization in the "RPA" instrument (at 170 ° C for 10 minutes ). The vulcanized samples were subjected to the measurement of the dynamic shear modulus (G ') at 70 ° C, frequency 10 Hz, deformation from 0.1% and 10%.

The dynamic elastic properties were expressed in terms of dynamic modulus with elastic shear (G '), viscous (G' ') and Tan delta (loss factor) (G' '/ G').

EXAMPLE 1

Preparation of activating fillers (ZnO / SiO2) according to the known art

ZnO / SiO2 activating fillers were prepared using the following procedure described in Chemical Engineering Journal 275 (2015) 245–252.

Powdered silica (0.426 mol, Rhodia Zeosil MP1165 precipitated silica, BET specific surface area 160 m <2> / g), was dispersed in 0.90 l anhydrous ethanol by sonication for 10 min (pulses: 1 s; 20 kHz ). Subsequently, to the silica suspension, Zn (CH3COO) 2.2H2O (quantity in Table 1) and NaOH (0.10 mol) were added under stirring, at 65 ° C:

Table 1

The ZnO nanoparticles, originated by hydrolysis, condensed on the surface of the silica forming samples with different amounts of zinc. After 20 minutes, the solid particles of ZnO / SiO2 were filtered, then washed four times with ethanol and dried in the air at room temperature.

EXAMPLE 2

Preparation of vulcanization activating fillers (ZnO / SiO2)

1.2 liters of ethanol, 4.7 g of NaOH and 8.9 g of zinc acetate dihydrate were added to a 3 liter flask with stirring, until complete dissolution. The solution thus obtained was heated up to 65 ° C, until it became milky due to the probable formation of zinc compounds of the [Zn (OH) n] <n +> type. 17.06 g of silica (Rhodia Zeosil MP1165, BET specific surface area 160 m <2> / g) were then added, maintaining the temperature at 65 ° C for 20 minutes under stirring. The suspension was then filtered on a filter, washing the solid with 200 ml of ethanol three times, finally drying the product in the air at room temperature.

19.4 g of solid consisting of silica nanoparticles were obtained, with a ZnO load equal to about 12.3% by weight.

EXAMPLE 3

Preparation of vulcanization activating fillers (ZnO / Sepiolite)

1 g of sepiolite was dispersed in 50 ml of 0.01 M NaOH and left under stirring at room temperature for 24 h. The dispersion was centrifuged at 9000 rpm for 30 min. The precipitate was dispersed several times in deionized water to allow optimal washing and recovered again by centrifugation to neutral pH. The solid was dried by lyophilization. In another flask, 140 ml of ethanol and 0.56 g of NaOH (conc. NaOH = 0.1 M) were added and left under stirring at 65 ° C for 10 min. After the dissolution of the soda, zinc acetate dihydrate (0.39 g) was added and left under stirring until the solution became cloudy. Finally 1 g of previously treated sepiolite was added and left under stirring for 20 minutes.

The product was filtered on a buchner, washed 3 times with fresh ethanol and dried in an oven overnight at 80 ° C.

Characterization of the vulcanization activating charges (D)

Samples of the activating fillers prepared in Example 2 were subjected to the following analyzes:

Table 2

EXAMPLE 4

Preparation of synthetic isoprene-based elastomeric compounds for substrate In this example we wanted to compare a conventional compound for substrate comprising a traditional filler (silica) and an activator (microcrystalline ZnO) (Comparative 4.1), a compound comprising an activating filler (ZnO / SiO2) but prepared according to a classical process with simultaneous addition of the silane (Comparative 4.2), a mixture comprising an activating filler (ZnO / SiO2) prepared by adding the silane together with said filler and only after the stearic acid (Comparative 4.3, as described in Chem. Eng, 2015, 245, page 247, par.2.4) and a compound according to the invention (Example 4.4), in which the silane was added in a subsequent step, when the stearic acid had completely reacted with the zinc of the activating charge.

The elastomeric compounds of Examples 4.1 - 4.4 below were prepared according to the methods described here. The quantities of the various components are indicated in phr and shown in the following Table 3:

Table 3

in which:

IR: synthetic polyisoprene with high cis content (min. 96%), obtained by polymerization in solution with Ziegler / Natta catalyst; Supplier NIZHNEKAMSKNEFTECHIM EXPORT;

Silica: ZEOSIL 1115 MP (BET specific surface area 95-120 m <2> / g, white microbeads obtained by precipitation from sodium silicate solutions with sulfuric acid. Does not contain crystalline silica. Supplier SOLVAY RHODIA OPERATIONS Ac. Stearic: Supplier TEMIX OLEO SRL

6PPD: N- (1,3-dimethylbutyl) -N`-phenyl-p-phenylenediamine, Supplier: SOLUTIA / EASTMAN

ZnO (80): 80% zinc oxide, 20% polymeric binder and dispersing agent, Supplier LANXESS ADD

silane: TESPD Bis- (3-triethoxy-silyl-propyl) -disulfide, Supplier JINGZHOU JIANGHAN FINE CHEM CBS: N-cyclohexyl-2-benzothiazylsulfenamide, cyclohexylamine content <1%, Supplier DUSLO

sulfur: Crystex OT33 amorphous sulfur, insoluble in CS2 and in toluene. 33% treated with hydrotreated heavy naphthenic distillate (petroleum), EASTMAN supplier.

The mixing was carried out in several stages using a Thermo Haake Reomix internal laboratory mixer with tangential rotors (250 ml mixing chamber).

In the first phase (1-0) the elastomeric polymers were introduced and chewed for 30 seconds at 60 ° C (set temperature).

In the following phase (1.1) the traditional filler, the antioxidant and possibly the stearic acid, the activating filler, the silane were added.

The mixing was continued for 2 minutes, until reaching 120 ° C ± 5 ° C.

After 12-24 hours, in the following phase (1.2) carried out using the same mixer, ZnO (Comparative 4.1) or the activating filler ZnO / SiO2 (Comparative 4.2, Comparative 4.3 and Invention 4.4) were eventually introduced, for Comparative 4.2 the silane and for Comparative 4.3 the ac. stearic. The mixing was continued for about 2 minutes, until the reaction between stearic acid and zinc was completed, reaching 125 ° C ± 5 ° C. In the subsequent phase 1.3, for some examples the silane was added and the mixing was prolonged for another 2-3 minutes, after which the compounds were discharged. After 12-24 hours, in phase (2), carried out using the same mixer, the vulcanizer (Sulfur) and the accelerator were introduced, and the mixing continued for about 2 minutes, until reaching 95 ° C ± 5 ° C, when the compounds have been discharged.

The elastomeric compounds 4.1 - 4.4 prepared above were evaluated for their behavior in vulcanization (170 ° C, 10 min.) And subsequently, in terms of static and dynamic mechanical properties, according to the methods previously described. The results of these tests, reparameterized considering the value obtained with Comparative 4.1 to be 100, are collected in the following Table 4:

Table 4

in which

MH (maximum torque): is the torque measured when the crosslinking can be considered complete;

MH-ML: difference between maximum torque MH and minimum torque ML;

T-MH: it is the time necessary to reach the complete crosslinking of the sample;

Tan D (hysteresis) was calculated as the ratio of the G '' / G 'modules (deformation of 9% at 70 ° C);

G '(9%) represents the shear modulus of elasticity measured at 70 ° C at a deformation amplitude of 9%;

G '(9%) represents the viscous shear modulus measured at 70 ° C at a deformation amplitude of 9%;

CR indicates the stress in correspondence of the elongation at break (MPa);

CA1 indicates the strain measured at 100% strain (MPa);

n.d. not measured.

From the values of MH, CR and CA1 reported in Table 4 it is highlighted that the activating filler ZnO / SiO2 guaranteed at least the same mechanical and kinetic vulcanization properties of the classic microcrystalline system of ZnO, with the same amount of Zn and filler (Invention 4.4 vs Comparative 4.1).

Moreover, thanks to the change in the order of addition of the ingredients of the present process, i.e. with the anticipated addition of the stearic acid in phase 1.1 and, in particular, the delayed introduction of the silane in phase 1.3, it was observed that the vulcanized compound of the invention (4.4) showed a significant decrease in tan D and viscous shear modulus (G '') at 70 ° C (10 Hz and 9%) of 46% and 53% respectively. These properties predict a decrease in rolling resistance during exercise, which results in an increase in tire mileage and therefore in greater environmental sustainability.

If, on the other hand, the silane was added simultaneously to the ZnO / SiO2 in phase 1.2, as in the compound of Comparative 4.2, the reduction of tan D and module G '' at 70 ° C was only 31% and 39%.

Comparative 4.3 shows the negative effects of adding ZnO / SiO2 together with silane, in particular on the G '' values at 70 ° C, where there is even an increase of 7% compared to the significant reduction (-53%) of the sample according to the invention (4.4).

EXAMPLE 5

Preparation of elastomeric compounds based on synthetic isoprene and polybutadiene for tire sidewall.

In this example we wanted to evaluate, with the same process according to the invention, the effect of the incorporation of the Zn / SiO2 filler with respect to the traditional ZnO on the vulcanization parameters and on the mechanical properties of a compound based on synthetic isoprene 40% and 60% high cis polybutadiene.

The elastomeric compounds of Examples 5.1 and 5.2 below were prepared according to the methods described herein. The quantities of the various components are indicated in phr and shown in the following Table 5:

Table 5

in which:

BR butadiene with high cis content (97.5%), polymerized with neodymium, Supplier ARLANXEO; and the other ingredients are the same as in the previous example 4.

The mixing was carried out in several stages as described in Example 4 by adding the ingredients in the quantities, in the phase and in the order indicated in Table 5, in particular by adding stearic acid early (1.1) and silane (1.3) late.

The elastomeric compounds 5.1 and 5.2 thus prepared were evaluated for their behavior in vulcanization (170 ° C, 10 min.) And subsequently, in terms of static and dynamic mechanical properties, according to the methods previously described. The results, reparameterized considering the value obtained with Comparative 5.1 to be 100, are collected in the following Table 6:

Table 6

in which

DG 'at 70 ° C, 10 Hz, 9% and 3% is the difference in shear modulus measured at 70 ° C at a strain amplitude of 9% or 3% respectively (predictive of rolling resistance) and the other parameters have the meaning shown above.

From the values of MH, G 'and DG' reported in Table 6 it is highlighted that, with the same preparation process and elastomeric polymers, the activating charge ZnO / SiO2 guaranteed good mechanical properties and a significant decrease in the hot, predictive tan Delta a decrease in the rolling resistance of the tire during operation.

In the process according to the invention (Inv. 5.2) there was also a significant decrease in the cross-linking time T-MH.

EXAMPLE 6

Preparation of elastomeric compounds based on synthetic isoprene and polybutadiene for tire sidewall

In this example we wanted to evaluate, with the same process according to the invention, the effect of the incorporation of the Zn / SiO2 filler with respect to the traditional ZnO on the vulcanization parameters and on the mechanical properties of a compound based on synthetic isoprene 40% and high cis 60% polybutadiene, in the presence of a vulcanization system different from the previous one.

The elastomeric compounds of Examples 6.1 and 6.2 below were prepared according to the methods described here. The quantities of the various components are indicated in phr and shown in the following Table 7:

Table 7

0 50% S on C 330,,

in which:

Carbon black CB: produced with the oven process, supplier ORION ENGINEERED CARBONS;

Wax: mixture of normal and iso paraffins, with bimodal distribution (it can contain a maximum of 1% of polyethylene PE), Supplier REPSOL LUBRICANTES Y ESPECIAL; TBBS: N-t-butyl-2-benzothiazylsulfenamide, supplier LANXESS; and the other ingredients are the same as in the previous examples.

The mixing was carried out in several phases as described in Example 4 by adding the ingredients in the quantities, in the phase and in the order indicated in Table 7, in particular by adding the stearic acid early (phase 1.1) and late the silane (phase 1.3 ).

The elastomeric compounds 6.1 and 6.2 thus prepared were evaluated as regards the type of crosslinking after vulcanization (170 ° C, 10 min.) And subsequently, in terms of static and dynamic mechanical properties, according to the methods described above. The results, reparameterized considering the value obtained with Comparative 6.1 to be 100, are collected in the following Table 8:

Table 8

From the values reported in Table 8 it is highlighted that, all variables being equal, including the vulcanization system, the activating charge ZnO / SiO2 and the methods of addition of the process of the invention guaranteed a significant decrease in the hot tan D together with an increase in mono- and disulfides, with a less hysteretic behavior of the compound, predicting a lower rolling resistance of the tire during operation.

EXAMPLE 7

Preparation of elastomeric compounds based on natural rubber for substrate In this example we wanted to evaluate the effect of the incorporation, according to the process of the invention, of the filler ZnO / SiO <2> with respect to the traditional ZnO, with the same filler and of zinc content, on the vulcanization parameters and on the mechanical properties of a compound based on natural rubber.

The elastomeric compounds of Examples 7.1 and 7.2 below were prepared according to the methods described here. The quantities of the various components are indicated in phr and shown in the following Table 9:

Table 9

()

in which:

NR: natural rubber (Natural rubber, cis 1,4-polyisoprene), SIR 20, supplier PT. KIRANA MUSI PERSADA, SFN;

ZnO: microcrystalline, white powder, supplier ZINCOL OXIDES;

TMQ: polymerized 2,2,4-trimethyl-1,2-dihydroquinoline, supplier LANXESS;

PVI: N-cyclohexylthiophthalimide, supplier SHANDONG YANGGU HUATAI CHEM, and the other ingredients are the same as the above examples.

The mixing was carried out in several phases as described in Example 4 by adding the ingredients in the quantities, in the phase and in the order indicated in Table 9, in particular by adding the stearic acid even more early (phase 1-0) and belatedly the silane (step 1.2).

The elastomeric compounds 7.1 and 7.2 thus prepared were evaluated with regard to the vulcanization parameters and subsequently, in terms of static and dynamic mechanical properties, according to the methods described above. The results, reparameterized considering the value obtained with Comparative 7.1 to be 100, are collected in the following Table 10:

Table 10

in which:

T30, T60, T90 and T-MH are the time required to reach respectively 30% (T30), 60% (T60), 90% (T90) and 100% (T-MH) of the maximum torque value (MH);

E 'is the viscous dynamic modulus of traction / compression,

It is the dynamic elastic modulus of traction / compression,

Tan delta is the ratio between the viscous dynamic modulus (E ") and the elastic dynamic modulus (E’),

AR is the elongation at break.

From the values reported in Table 10 it is highlighted that, all other variables being equal, the activating charge ZnO / SiO2 gave the compound of the invention of Example 7.2 better static mechanical properties (CR and AR, respectively increased by 14% and 17%) and a faster vulcanization kinetics than the Compound of Comparative 7.1, comprising conventional microcrystalline ZnO (compare the values of T30, T60, T90 and T-MH). The differences in the vulcanization kinetics can be appreciated from the trend of the curves of the graph shown in Figure 5.

The ZnO / SiO2 activating charge and the preparation process according to the invention led to an increase in the hysteresis at the temperatures of 23 ° C and 10 ° C of the vulcanized compounds, with a corresponding increase in the E '' module, predictors of better performance. of the tire in wet conditions. Otherwise at 100 ° C a hysteresis similar to the reference was observed, predicting a comparable resistance to rolling and abrasion of the tire during operation.

EXAMPLE 8

Preparation of elastomeric compounds based on natural rubber for substrate In this example we wanted to compare two comparative compounds for substrate - comprising traditional filler (silica) and activator (microcrystalline ZnO) (Comparatives 8.1 and 8.2) prepared the first according to the present process with addition early phase of ZnO and silica and later of silane (phase 1.2) and the second with a different process, in which silane and silica are introduced initially in phase 1.1 and ZnO and stearic acid subsequently in phase 2.0 - with a mixture according to the invention, comprising instead the activating filler ZnO / SiO2 (D) and prepared with the late addition of the silane (step 1.2) (Invention 8.3). The elastomeric compounds of Examples 8.1 - 8.3 below were prepared according to the methods described here. The quantities of the various components are indicated in phr and shown in the following Table 11:

Table 11

in which the ingredients are the same as in the previous examples.

The mixing was carried out in several phases as described in Example 4 by adding the ingredients, in the quantities, in the phase and in the order indicated in Table 11.

The elastomeric compounds 8.1 - 8.3 thus prepared were evaluated with regard to the vulcanization parameters and subsequently, in terms of static and dynamic mechanical properties, according to the methods described above. The results, reparameterized considering the values obtained with Comparative 8.1 to be 100, are collected in the following Table12:

Table 12

From the values reported in Table 12 it is highlighted that, all other variables being equal, the compound of the invention (Example 8.3, process of the invention, activating filler ZnO / SiO2) compared to the comparative compounds of Example 8.1 (process of the invention but classic microcrystalline ZnO) and Es. 8.2 (standard process and classic microcrystalline ZnO) showed an increase in hysteresis at 10 ° C and 23 ° C, with an increase in the E '' module, predicting a good behavior of the tire in the wet and a significant reduction at high temperatures ( 100 ° C), mainly due to the decrease in the E '' modulus, predictive instead of improved rolling resistance and abrasion resistance of the tire in use.

Furthermore, the compound of the invention Ex. 8.3 showed a significant decrease in the vulcanization time (see the values of T30 - T90).

Considering the vulcanization times reported in Table 12 (T30 - T90), an increase was observed when passing from a standard compound (Comparative Ex.

8.2, classical zinc process and compound) to the mixture of Ex. Comparative 8.1 (process of the invention and compound of classical zinc) to indicate how the late addition of the compatibilizing agent characterizing the present process does not in itself lead to an increase in the cross-linking speed but, surprisingly, only in the specific case of use of zinc in the form of ZnO / SiO2 activating filler.

The differences in vulcanization kinetics can also be appreciated from the trend of the curves of the graph shown in Figure 6.

Fig.6 shows the normalized curve of the torque values [(Sx-Smin) / (Smax-Smin) * 100] measured over time (min.) During vulcanization at 170 ° C for 10 min. of the vulcanizable compound according to the invention of Es. 8.3 compared to the comparative compounds of Ex. 8.1 and 8.2. As can be seen, the sample of the invention 8.3 shows the faster vulcanization kinetics than both comparatives 8.2 and 8.1.

It is also noted how the microcrystalline zinc inserted in phase 1.1. of the Es 8.1 results in the slowest kinetics.

Claims (18)

CLAIMS 1. A process for the preparation of a vulcanizable elastomeric compound for tires, said process comprising at least: - a mixing step (1) of at least one elastomeric polymer (A) and of at least one additive for elastomeric blends, with the exception of the vulcanizing agents (B), to give a non-vulcanizable elastomeric blend; - a mixing step (2) of the non-vulcanizable elastomeric blend and at least one vulcanizing agent (B), to give a vulcanizable elastomeric blend, and - an unloading phase of the vulcanizable elastomeric compound, wherein in the mixing steps (1) and / or (2) at least one fatty acid (C), at least one compound (D) comprising zinc directly bound to a white filler and at least one compatibilizing agent (E) are added, characterized in that said at least one compatibilizing agent (E), is added after the complete addition and processing, of said at least one fatty acid (C) and at least one compound (D) comprising zinc directly bound to a white filler. The process according to claim 1 wherein said at least one fatty acid (C), at least one compound (D) comprising zinc directly bound to a white filler and at least one compatibilizing agent (E) are all added in the mixing step (1 ). The process according to claim 1 wherein said at least one fatty acid (C) and at least one compound (D) comprising zinc directly bound to a white filler are added in the mixing step (1) and said at least one compatibilizing agent (E ) is added in the mixing step (2). The process according to any one of the preceding claims in which the processing of said at least one fatty acid (C) and at least one compound (D) comprising zinc directly bound to a white filler is carried out at a mixing temperature at least equal to the temperature of fusion of said fatty acid (C) or higher. The process according to any one of the preceding claims in which said mixing step (2) is carried out at a mixing temperature lower than 160 ° C, preferably at 140 ° C, more preferably at 120 ° C. The process according to any one of the preceding claims in which: - said diene elastomeric polymer (A) is selected from cis-1,4-polyisoprene, 3,4-polyisoprene, polybutadiene, possibly halogenated isoprene / isobutene copolymers, 1,3-butadiene / acrylonitrile copolymers, styrene / 1 copolymers , 3-butadiene, styrene / isoprene / 1,3-butadiene copolymers, styrene / 1,3-butadiene / acrylonitrile copolymers and mixtures thereof; and / or - said vulcanizing agent (B) is selected from sulfur and sulfur donors selected from caprolactam disulfide (CLD), bis [(trialkoxysilyl) propyl] polysulphides, dithiophosphates, phosphoryl polysulfide (SDT) and their mixtures. 7. The process according to any one of the preceding claims, in which said fatty acid (C) is selected from the saturated or unsaturated fatty acids containing from 8 to 26 carbon atoms, their esters, their salts and their mixtures, is preferably selected from acid lauric (C12), myristic acid (C14), palmitic acid (C16), stearic acid (C18), behenic acid (C22), lignoceric acid (C24) and their mixtures, more preferably it is stearic acid. The process according to any one of the preceding claims in which the zinc in said compound (D) is present as zinc oxide, preferably as zinc oxide in particles of average size between 3 nm and 100 nm, more preferably between 4 and 10 nm. The process according to any one of the preceding claims in which said white filler of said compound (D) is selected from silica and silicates selected from bentonite, nontronite, beidellite, volkonskoite, hectorite, saponite, sauconite, vermiculite, sericite, sepiolite, paligorskite or attapulgite, montmorillonite, alloisite, possibly modified by acid treatment and / or derivatized, and their mixtures, more preferably it is silica. The process according to any one of the preceding claims wherein said compound (D) comprising zinc directly bonded to a white filler is zinc oxide on silica. 11. The process according to any one of the preceding claims, wherein said compatibilizing agent (E) is a silane selected from among those having at least one hydrolyzable group, of general formula (I): (R) 3Si-CnH2n-X (I) where the R groups, which may be identical or different, are selected from alkyl, alkoxy or aryloxy or halogen groups, provided that at least one of the R groups is an alkoxy or aryloxy group or a halogen; n is an integer from 1 to 6 inclusive; X is a group chosen from: nitrous, mercapto, amino, epoxide, vinyl, imide, chlorine, - (S) mCnH2n-Si- (R) 3 and -S-COR, where m and n are integers from 1 to 6 inclusive and i R groups are defined as above. The process according to any one of the preceding claims wherein: - said fatty acid (C) is added in a total amount comprised between 0.05 and 20 phr, preferably between 0.1 and 15 phr, more preferably between 0.5 and 5 phr; - said compound (D) comprising zinc directly bound to a white filler is added in a total amount comprised between 1 and 100 phr, preferably between 5 and 80 phr, more preferably between 10 and 30 phr; And - said compatibilizing agent (E) is added in a total amount comprised between 0.1 phr and 20 phr, preferably between 0.5 phr and 10 phr. 13. The process according to any one of the preceding claims in which one or more further additives are added selected from accelerating vulcanization (F), retarding vulcanization (G), reinforcing fillers (H), antioxidants (I), waxes (L ) and plasticizers (M). 14. A vulcanizable elastomeric blend obtained according to the process of any one of the preceding claims. The vulcanizable elastomeric blend according to claim 14 comprising zinc in an amount lower than 4 phr, preferably lower than 3 phr, more preferably lower than 2 phr. 16. A tire component comprising the vulcanizable blend according to claims 14 or 15 or the vulcanized blend obtained by its vulcanization. 17. The tire component according to claim 16 selected from tread band, substrate, anti-abrasive strip, sidewall, side insert, mini-sidewall, underliner, rubber layers, bead filler and sheet, preferably between underlayer and sidewall. A vehicle wheel tire comprising at least one tire component according to claims 16 or 17.